THIS INVENTION relates to equipment for pre-tensioned or post-tensioned prestressed cementitious structures and more particularly to means for anchoring and coupling the ends of cables used in such structures.
In this specification, the term "cable" is used in a broad sense so as to include in the scope of its meaning wires, strands and cables in general.
In the post-stressing of concrete structures, cables are placed in position prior to pouring of the concrete. Protective sheaths are located around the cables so that the latter may be elongated, under tension, within the concrete. After the concrete is poured a tensioning force is applied to the cables which are anchored at each end to the concrete to induce a compressive force in the structure.
A generally accepted method of poststressing involves anchoring one end into the structure, called the dead end anchor, and applying the tension to the other end of the cables which are subsequently held in position by a cable anchor. One such anchor which is very effective in use is that described in U.S. Pat. No. 3,983,606.
The dead end anchor can conveniently be formed by making the cables extend through the structure as a long loop with the looped end of the cables exposed from the sheath and located around vertical rods which are buried in the concrete. These looped cables enable a very inexpensive but positive dead end anchor to be obtained.
Furthermore, it is often required to couple together cable ends protruding toward one another from adjacent structures and to apply a tensioning force to the joined cables. This is particularly the case in continuous span beams used in bridges and other concrete structural work.
The coupling of contiguous reinforcing cables is usually a somewhat difficult operation and most couplers are expensive units.
For example there is the anchor-coupler type unit described in U.S. Pat. No. 3,973,297 wherein ends of cables are inserted into blind passages containing spring loaded wedge assemblies adapted to automatically prevent withdrawal of the cables.
In alternative arrangements separate couplers are used for each cable wherein the ends of such contiguous cables are each fitted into an anchor assembly and the anchor assemblies located in an axially extending tubular member. These assemblies usually require expensive machine operations in their production.
Couplers comprising housings having oppositely directed tapered passages therein into which wedges are introduced to secure the contiguous cables have been effectively used but their assembly is a tedious operation.